As methods for directly separating and analyzing enantiomer mixtures of compounds containing an asymmetric carbon atom using optically active compound-grafted packing materials by means of liquid chromatography, there have been reported heretofore a method comprising ligand exchange using optically active proline-grafted packing materials by Davankov et al.; a method involving electron transfer complexes using .pi.-electron-lacking, optically active compound-grafted packing materials by Gil-Av et al.; a method involving separation of N-acylated amino acid esters or N-acylated dipeptide esters using optically active N-acylated amino acid-grafted packing materials by Hara et al.; a method involving separation of 3,5-dinitrobenzoylated amino acids, amines, hydroxy acids, sulfoxides, etc. using optically active 1-(9-anthryl)trifluoroethanol-grafted packing materials, or a method involving separation of aromatic alcohols using 3,5-dinitrobenzylated, optically active phenylglycine-grafted packing materials by Pirkle et al.; and so on. In these methods, however, the compounds capable of being separated are limited to a narrow range, the degree of separation is poor, or grafted packing materials are produced with difficulty so that packing materials having good reproducibility in the quality, etc. are difficult to produce. It cannot thus be said that these packing materials are practical.
As a result of extensive investigations in an attempt to develop grafted packing materials which are widely applicable to compounds to be analyzed, are relatively easily prepared, are chemically stable and are practical, the present inventors have found that packing materials for chromatographic use obtained by grafting organosilane derivatives selected from the group consisting of urea derivatives obtained by reacting optically active isocyanates with aminoalkylsilanes, N-carbamoyl amino acid derivatives obtained by reacting optically active amino acids carbamoylated by isocyanate with aminoalkylsilanes, and O-carbamoyl hydroxy acid derivatives obtained by reacting optically active hydroxy acids carbamoylated by isocyanate with aminoalkylsilanes, on inorganic carriers having hydroxyl groups at the surface thereof are extremely useful since they not only exhibit an excellent effect for separating enantiomer mixtures of compounds containing an --OH group, a --CONH-- group, ##STR5## a --COO-- group, an --NHCOO-- group, an --NHCONH-- group or ##STR6## bonded to an asymmetric carbon atom thereof, but also can easily be prepared by ordinary chemical reactions and are chemically stable, and have reached the present invention.